A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Hotan area, one of the five regions of Xinjiang Uygur Autonomous region, is based in Hotan City. Located in the southern corner of Xinjiang Uygur Autonomous region, the center is located at 79.92 °east longitude and 37.12 °north latitude, reaching the border between Kunlun Mountains and Tibet Autonomous region to the south, Taklimakan Desert to the north and Aksu to the north, Bayingol Mongolia Autonomous Prefecture to the east, Kashmir to the west, Karakoram Mountains to the southwest and Kashmir to the southwest. It is about 670 km long from east to west and 570 km wide from north to south. The total area is 247800 square kilometers. Hotan area is a typical inland arid area, located in the hinterland of Eurasia, with an arid and desert climate. There are 36 large and small rivers. It is an area rich in light energy resources in China. It is famous for its rich in Hetian jade.